'79 kz1000 fresh rebuild but wont fire off and run

with 1 cam being 180 degrees out that means both valves were trying to open at same time and tried pushing each other out of the way and something gave,somebody else had same problem recently on here

originated by a bunch of drunk disoriented japanese pilots in wwII,carried on to this day by a bunch of disoriented valves in certain japanese motorcycle engines with same basic result

Since I recently went through this process myself.... have some questions... Maybe I'm just not fully understanding....

Here we go...

Compression seems low:
What are the measured values of each cylinder?

In your build, are you using stock or performance cams?

If performance cams, are you using adjustable cam sprockets?

If performance cams, are you positive you have them degreed correctly?

NOTE: This one bit me where I had them dialed in, after a run or two, re-checked them and the intake was off by 13 degrees.

NOTE 2: In reviewing my project posting of this, you'll find where my compression was low and this is what led me to re-checking everything and that's where I found my cams off....

Now since I just went through the process of carb jetting for emissions.... popping out the exhaust can also be caused by too lean of settings, especially in your pilot/air/screw mixtures.

Again, just went through this last night where I had them too lean where it ran like crap (no power, popping) on the way to the emissions and it wouldn't start in the emissions bay! lol!.... rolled her out of the bay, re-adjust the pilots for a tad more rich, re-adjust the idle and she flew through just fine...

And for the others, of course I re-set them (pilots) back to normal operations.... :laugh:

Another thing you didn't mention was the ignition/timing.... Truly doesn't have anything to do with compression so this question is more towards the popping...

A full compression test & leak down test will inform you of where you truly stand....

And as the others have mentioned, double check your valve clearances....

Let's see, did I forget anything.... Hmmm, oh well that should be a good start for you....

OMR

Yes, the compression seems low b/c it wont even blow ur finger off the spark plug hole. We are using the original stock factory cams, my uncle says that the valves are set to the factory specs, there shouldnt be a problem with it being to lean b/c we have been using starting fluid and carb cleaner to try to get it to fire of along with gasoline.

is the head re-done?...stock pistons?..points or electonic ignition?.....the more info the better....

it's all factory cams and rings not actually rebuilt we put new stock rings and gaskets transistorized

Almost forgot... Rings rotated & staggered to spec?

unknown someone else put motor together and it still isn't running

reading this one close...spent two hours trying to start one i just re-did top end on...pulled it just now and put the old motor back in.....popped once throught the left carb filter and has spark....not jumping on your thread...just that i am in the same boat.....carry on brothers...craig

With a leak down test, you'll be able to hear the air escape.... Troubleshoot to source of leakage...

Based on what you have provided... Either rings or valves are going to loose that much air where you can't even feel it (finger spark plug hole)...

Unless it's escaping at the cylinder base gasket or head base gasket... :ohmy:

You have mentioned numerous times seems low... What exactly are you measuring in each cylinder in your compression tests?

well then.... Only one way to confirm now, open her up....

Just don't see any magical response that could possibly confirm otherwise...

And for God's sake, don't start this motor again until you perform the leak down test or at least open her up for visual confirmations... You may just have got lucky and not bent a valve or two...

Let us know what you find....

:S compression shows 5-10 pounds if that much I am thinking you are probably right will have to crack it open and check it all out thanks for the advice will definitely be on here with many more questions as we go forward

PLUMMEN wrote:

if its the rings that are leaking that bad you should hear lots of air coming out crankcase vent under carbs.if cam was 180 out and motor was turned over im betting the intake/exhuast valves took themselves out

I'll second that motion. Cylinders 1&4 won't care if the intake cam is out 180 when it's bolted in. Those lobes won't cause a problem just yet. Both pistons are on TDC. #4 should be on end of exhaust stroke if that cam is timed properly.

If cams were put in as described, intake 180* off, when the crank is rotated forward 180* to BDC for 1&4, both lobes for #4 cylinder will be about 12 o'clock position. Cams would have traveled 90 *. Rotate the crank another 180* to TDC and what happens?

Exhaust lobe and intake lobe would now be at 3 o'clock position on #4 cylinder. Both valves opening at the same time.....

Not Good

If that is the scenario, the head needs to come off and apart. In addition to the bent valves, there may be broken or cracked valve guides. In fact, I can about guarantee that. I've seen this scenario in cylinderheads so many times over the years..

It's just plain sad when things like this happen.